CN101726359B - Multiple-grating monochrometer and calibration method thereof - Google Patents
Multiple-grating monochrometer and calibration method thereof Download PDFInfo
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- CN101726359B CN101726359B CN2008102254242A CN200810225424A CN101726359B CN 101726359 B CN101726359 B CN 101726359B CN 2008102254242 A CN2008102254242 A CN 2008102254242A CN 200810225424 A CN200810225424 A CN 200810225424A CN 101726359 B CN101726359 B CN 101726359B
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Abstract
The invention discloses a multiple-grating monochrometer. The monochrometer mainly comprises a mono-light optical splitting system, a control system, a computer and a printer, wherein the splitting system and the control system are designed as one, the upper part of the device is a grating chamber, the lower part is a controller chamber; the grating chamber mainly comprises an entrance slit, two exit slits, a color filter group, two concave mirrors, a grating turntable, a reflector and a stepper motor, wherein the open or close size of the entrance and exit slits are controlled manually; the hardware circuit adopts a second-order Butterworth filter to perform anti-aliasing filtering, and the hardware 8-bit pulse width modulation method is used to realize the control of the stepper motor. The multiple-grating monochrometer overcomes the bottleneck of low data transmission speed caused by the use of the RS232 interface before and the USB2.0 interface is used to connect with the computer. A power distribution system, a grating turntable control system, a filtering wheel control system, a reflector control system and a high speed and high accuracy data acquisition system are integrated to increase the integration degree, reliability, control precision and scanning precision of the system. The newly provided automatic scanning multiple-grating monochromatic spectrometer system has wide development prospect.
Description
Technical field
The present invention relates to a kind of spectral analysis and measuring technique, particularly a kind of multiple-grating monochrometer and calibrating method thereof.
Background technology
Monochromator is a kind ofly by the grating diffration effect a branch of complex light to be decomposed into the monochromatic spectroscopic instruments of different wave length, is the important foundation instrument that optics and optoelectronic areas carry out spectral analysis and measurement.Because the high speed development of electronic technology, photoelectric detecting technology is had higher requirement in the resolution of instrument, measurement range, measurement sensitivity, measuring speed and aspect such as integrated, integrated.The wavelength scanning range, speed, precision and the integrated level that improve the monochromatic light spectrometer are the main tasks of present monochromatic light spectrometer Control System Design.The automatic grating monochromatic light of computer control originally spectrometer adopts sine mechanism more, a grating can only be installed, the scanning optical spectrum narrow range; Sine mechanism can only move reciprocatingly in addition, collides easily, adopts the grating monochromatic light spectrometer trend on the verge of being replaced of sine mechanism.
Summary of the invention
The objective of the invention is provides a kind of raising wavelength scanning range and scanning accuracy for the deficiency that solves above-mentioned technology, has the multiple-grating monochrometer and the calibrating method thereof of higher reliability, integrated level and automaticity.
In order to achieve the above object, a kind of multiple-grating monochrometer that the present invention is designed mainly comprises monochromatic beam splitting system, control system, computing machine and printer, it is characterized in that monochromatic beam splitting system and Control System Design are one, instrument top is grating chamber, and the bottom is the controller chamber; Grating chamber mainly comprises an entrance slit, two exit slits, color filter group, two concave mirrors, grating turntable, reflective mirror and stepper motors, and the folding size of incident and exit slit is by manual control; Hardware circuit adopts second order Butterworth wave filter to carry out anti-aliasing filter, eliminates 200KHz with upper frequency, adopts the extreme value filter method to eliminate by the 50Hz power frequency of light source power supply system introducing in the software design and disturbs; Use 8 width modulations of hardware (PWM) method to realize to Stepping Motor Control, negative edge in pulsewidth output produces hardware interrupts, interrupt service routine withdraws from after starting the AD conversion, by AD conversion interrupt service routine sampled result is sent into the data buffering formation behind the AD EOC, realize multi-task mechanism by hardware mode, improved control and scanning accuracy greatly.
A kind of multiple-grating monochrometer that the present invention is designed can as wavelength coverage, signal intensity etc., be installed two kinds of receivers according to test request at two exit slits, simultaneously as CCD, photomultiplier, photoelectric cell, indium gallium arsenic or vulcanized lead etc.; Select monochromatic exit direction and corresponding data acquisition passage by the software control reflective mirror, largely reduced the trouble of changing receiver, increase wavelength scanning range.Because grating diffration efficient reduces gradually along with the increase that departs from the blaze wavelength region distance, to such an extent as to depart from the blaze wavelength district than far-end detector is surveyed less than signal.The color filter that six groups of color filters that incident light spectrum is filtered are installed at the entrance slit place is taken turns, and eliminates the influence of the above diffraction light of secondary, and this color filter wheel can be according to wavelength coverage by the automatic selection of software control or by artificial selection.Two spherical mirrors are mainly realized the focusing and the reflection of light.The grating of an above different wavelength range is installed on the grating turntable, as polylith gratings such as 300g/mm, 600g/mm, 1200g/mm and 2400g/mm, the grating turntable adds worm and gear by stepper motor and drives, realization is installed the attainable wavelength control precision of different gratings to the dispersion interaction of incident light; The pulpit is mainly by control circuit, and stepper motor driver and power supply are formed.
A kind of multiple-grating monochrometer that the present invention is designed, control is gathered integrated, do not need independent control box and data acquisition unit, the design of control circuit and data acquisition circuit merges on the circuit, and will control and Acquisition Circuit is installed in the bottom of monochromator casing; Improved integrated level; Control system adopts the usb bus interface to connect computing machine, by computer realization to the real-time control of grating turntable, color filter automatically or manual switching, the optional exit direction of software; Integrated signal gathering unit can be gathered voltage or current signal, has 1～256 times of programmable-gain, has the trigger port of two-way simultaneously, realizes the real-time control and the high speed spectrum data scanning of automatic grating monochromator.
A kind of multiple-grating monochrometer that the present invention is designed, described grating turntable adopts three optical grating constructions, realizes the autoscan of ultraviolet to infrared spectrum.Between the 3rd block of grating and first block of grating, the catch that the pattern zero point location uses is installed; Control system is that core realizes adopting USB interface to be connected with computing machine to the control and the double channel data acquisition of grating turntable, color filter wheel, reflective mirror with the C8051F060 single-chip microcomputer; The automatic switchover and the software programmable gain of electric current and voltage can be realized in the signal condition unit, can connect photomultiplier, the multiple receiver of photoelectric cell.System has advantages such as sampling precision height, integrated level height, automaticity height and sweep velocity be fast.
In order to reach goal of the invention, the calibrating method of a kind of multiple-grating monochrometer provided by the invention, it comprises uses grating monochromator to be calibrated and calibration software, with photomultiplier as receiver, it is characterized in that mercury lamp standard spectral line is carried out continuous sweep, constant B and S0 among formula S=Aarcsin (B λ)+S0 are demarcated, and use the standard spectral line of sodium vapor lamp that calibration result is verified.Wherein λ is an outgoing light wavelength behind monochromator splitting, the step number of pairing stepper motor when S is λ for the outgoing wavelength, A is for to segment the determined constant of stepper motor step angle when by worm gear transmission ratio, stepper motor, B is the constant of being determined by grating constant and monochromator light path system, S0 be grating by mechanical zero rotate to the zero order light position the stepper motor steps that should walk.Constant A can obtain by calculating in the formula, and constant B and S0 need to obtain by calibrating method; Use formula S=Aarcsin (B λ)+S0 to realize the accurate wavelength control of grating monochromator.
The calibrating method of described a kind of multiple-grating monochrometer is characterized in that catch that the pattern zero point location of the grating monochromator will be newly installed uses is installed between the 3rd block of grating and the first block of grating; At first the grating turntable is repositioned to mechanical zero before each scanning, be that the control step motor makes the catch on the grating turntable rotate to the optocoupler position, serve as control step motor rotation at interval with 16 steps then, the grating turntable is rotated a circle, come back to the optocoupler position up to locating stop piece, promptly use three blocks of gratings to finish scanning respectively same mercury lamp spectrum; In the scanning process, calibration software is with step number and gather numerical value with the real-time reading scan result of two-dimensional curve form, wherein horizontal ordinate is a step number, and ordinate is a spectral energy, and stepper motor is begun the step number walked by mechanical zero and the spectrum numerical value of collection saves as text; After run-down is finished, use calibration software that the data and curves that obtains is divided into three parts and analyze respectively, these three sections curves are respectively the scanning result of three pairing mercury lamp spectral lines of grating; At each section curve, with the strongest spectral position of the energy that occurs at first as zero order light, take this as the standard, the spectral line of close zero order light is the pairing spectral line of purple light 404.66nm, be respectively each bar spectral line such as 435.84nm, 546.07nm, 576.96nm and 579.07nm by that analogy, will comprise that the pairing stepper motor steps of each bar spectral line of zero order light is noted; Three blocks of gratings of quick acquisition zero order light separately that can be rough by above method scanning reaches and the pairing stepper motor steps of mercury lamp standard spectral line; Then at every block of grating, be the center with determined zero order light of said method and the pairing stepper motor steps of each standard spectral line respectively, at interval [S-128, S+128] serve as to rescan every spectral line at interval in the scope with a step, number of motor steps and corresponding spectral line collection result are noted, and therefrom find out maximal value, this process repeats 10 times, to obtaining 10 groups of stepper motor steps by position of spectral line, that 10 groups of numbers are average back as the final pairing stepper motor steps of this spectral line with the intermediate value method of average; It is pairing for obtaining the step number S that mercury lamp standard line wavelength should be walked to obtain every block of grating installing respectively by above method; To every block of grating, with the stepper motor steps mean value of zero order light correspondence as S0, bring the step number mean value and the wavelength of each bar spectral line correspondence into formula B=(sin (S-S0/A))/λ, parameter A is determined by machinery segmentation and electric segmentation ratio, calculate the pairing B parameter of each standard spectral line respectively, undertaken after the geometric mean as the B parameter of using in the final formula by 5 B parameter then; Simultaneously, after parameters is determined in the formula, use two spectral lines 589 and 589.6 of low-pressure sodium lamp formula to be calibrated as the calibration spectral line.Experimental result shows, segments multiple-grating monochrometer for 180: 1 machinery segmentations and 64: 1 electricity, can reach required bearing accuracy fully.
The multiple-grating monochrometer that the present invention proposes is gear train with the worm and gear, can rotate by 360 degree, can not produce the phenomenon of collision, and one to three block of grating can be installed on the grating turntable, has reduced the trouble of changing grating when improving wavelength scanning range.Combine by the machinery segmentation of the employing worm and gear kind of drive and the electricity segmentation of stepper motor driver, improved the wavelength control precision.For overcome the low bottleneck of data rate that adopts the RS232 interface in the past, adopt the USB2.0 interface to be connected with computing machine.Power distribution system, grating rotating platform control system, color filter cranking wheel control system, reflective mirror control system and high speed, the high-precision data acquisition system integration are improved together integrated level, reliability, control accuracy and the scanning accuracy of system.New many gratings of the autoscan monochromatic spectrum instrument system that proposes has vast potential for future development.
Description of drawings
Fig. 1 is the multiple-grating monochrometer overall construction drawing;
Fig. 2 is the grating chamber cut-away view;
Fig. 3 is the hardware system composition diagram;
Fig. 4 is a power distribution scheme block diagram;
Fig. 5 is stepper motor driver interface circuit and optocoupler testing circuit figure;
Fig. 6 is that electric current and voltage switches and differential amplifier circuit figure;
Fig. 7 is signal sampling channel theory of constitution figure;
Fig. 8 frequency overlapped-resistable filter circuit theory diagrams;
Fig. 9 is usb circuit figure;
Figure 10 is wavelength 579.96 and 10 result curve figure of 579.07 places multiple scanning before the filtering;
Figure 11 is wavelength 579.96 and 10 result curve figure of 579.07 places multiple scanning after the filtering;
Figure 12 is a sodium vapor lamp standard spectrum line chart;
Figure 13 is the length scanning accuracy table;
Figure 14 is 1200 ruling grating mercury lamp standard spectral line and step number mapping tables;
Figure 15 is each position of spectral line table.
Wherein: monochromatic beam splitting system 1, grating chamber 1-1, control system 2, controller chamber 2-1, computing machine 3, entrance slit 4, exit slit 5, color filter 6, color filter stepper motor 6-1, concave mirror 7, grating turntable 8, reflective mirror 9, reflective mirror stepper motor 9-1, color filter wheel 11, grating 12, worm gear 13-1, worm screw 13-2, worm drive stepper motor 13-3, control circuit 14, stepper motor driver 15.
Embodiment
The invention will be further described in conjunction with the accompanying drawings below by embodiment.
Embodiment:
As shown in Figure 1, a kind of multiple-grating monochrometer that present embodiment is described, mainly comprise monochromatic beam splitting system 1, control system 2, computing machine 3, computing machine 3 can connect printer, in order to improve the integrated and integrated of instrument, monochromatic beam splitting system 1 is designed to one with control system 2, and instrument top is grating chamber 1-1, and the bottom is controller chamber 2-1.Shown in Figure 2, grating chamber 1-1 mainly comprises an entrance slit 4, two exit slits 5, color filter 6, two concave mirrors 7, grating turntable 8, reflective mirror 9 and stepper motors 10, the folding size of entrance slit 4 and exit slit 5 is by manual control, two exit slits 5 can be installed two kinds of receivers simultaneously according to test request (as wavelength coverage, signal intensity etc.), as CCD, photomultiplier, photoelectric cell, indium gallium arsenic or vulcanized lead etc.; Select monochromatic exit direction and corresponding data acquisition passage by software control reflective mirror 9, largely reduced the trouble of changing receiver, increase wavelength scanning range.Because grating diffration efficient reduces gradually along with the increase that departs from the blaze wavelength region distance, to such an extent as to depart from the blaze wavelength district than far-end detector is surveyed less than signal.At entrance slit 4 places the 11 pairs of incident light spectrum of color filter wheel with six groups of color filters 6 are installed and filter, eliminate the influence of the above diffraction light of secondary, this color filter wheel 11 can be selected by software control or by artificial selection automatically according to wavelength coverage.Two concave mirror 7 main focusing and reflections that realize light.
To the real-time control of grating turntable 8, the automatic or manual switchover of color filter 6, optional exit direction of software and the configurable spectroscopic data of software are gathered in real time by computer realization in the multiple-grating monochrometer requirement.Grating turntable 8 can wavelength coverage as required be installed polylith gratings such as 300g/mm, 600g/mm, 1200g/mm and 2400g/mm, present embodiment is equipped with three blocks of gratings 12 on grating turntable 8, by worm drive stepper motor 13-3 add worm gear 13-1, worm screw 13-2 drives, and realizes the dispersion interaction to incident light.Pulpit 2-1 is mainly by control circuit 14, and stepper motor driver 15 and power supply are formed.The attainable wavelength control precision of different gratings is installed, as shown in figure 13.
The wavelength minimum resolution is 0.005nm when for example using the 1200g/mm grating, worm gear transmission ratio is 180: 1, stepper motor driver segmentation is than being 64: 1, according to optical grating diffraction formula (1), get m=1, d=1/1200 is during θ=19.3 °, calculate Δ λ ≈ 0.00043nm, satisfy accuracy requirement fully.Part of data acquisition requires to can be configured to the curtage input mode, has 1～256 times of programmable-gain, has the trigger port of two-way simultaneously.Control system adopts the usb bus interface to connect computing machine, has realized controlling in real time automatically and high speed spectrum data scanning of multiple-grating monochrometer.
Its hardware system: the C8051F060 that system adopts is fully-integrated mixed signal SOC (system on a chip) type MCU, and it adopts pipeline organization CIP-51 kernel, compare instruction execution speed with standard 8051 structures and improve a lot, and instruction set and MSC51 is compatible fully.When the CIP-51 kernel was operated in maximum system clock frequency 25MHz, its peak performance reached 25MIPS.Aboundresources on the C8051F060 sheet has 59 Digital I pins; Two 16, the ADC of 1Msps, and have dma controller; Two 12 DAC have the programmable data way of output; But 64KB in-system programming Flash storer, 4352 byte ram in slice; The external data memory interface of addressable 64KB address space etc.Select C8051F060 can obviously improve system running speed and integrated level satisfying under the situation of system requirements as core controller.Control system mainly contains compositions such as stepper motor driver interface, analog signal conditioner, expansion 32KB RAM, usb circuit, RS232 interface circuit and debug i/f circuit, and The general frame as shown in Figure 1.
For power supply: the grating monochromator control system contains stepper motor driving circuit, digital circuit and mimic channel automatically, and each several part needs different power supplies.The stepper motor power that drives the grating turntable is bigger, requires the 24V-1.5A power supply; The stepper motor power that drives color filter wheel and reflective mirror is less, needs the 12V-0.4A power supply; Stepper motor driver needs+5V power supply; Single-chip microcomputer and peripheral circuit needs+3.3V power supply, mimic channel employing ± 5V power supply.In order to reduce system bulk and power consumption, select for use to have the Switching Power Supply of 24V2A and the output of 12V1A two-way.The working power of each stepper motor is directly supplied with through the PCB circuit board by Switching Power Supply.By the 12V1A out-put supply through switching power source chip LM2576 conversion acquisition+5V power supply, be respectively stepper motor driver, numeral and mimic channel power supply is provided, because the stepper motor working current is big, interference to ground wire is very big, its work and control power supply need be isolated with digital circuit and mimic channel power supply, employing has the integrated DCDC that input and output isolate mutually and obtains numeral and mimic channel power supply respectively, and translation circuit as shown in Figure 4.By the conversion of NR5S5DC-DC module obtain that the TTL circuit needs+the 5V power supply, use LM117 low pressure difference linearity Voltage stabilizing module step-down acquisitions+3.3V voltage then, by NR5D5 module acquisition mimic channel required ± the 5V power supply.
For motor-driven: the drive part of grating turntable is selected gloomy wound two-phase hybrid stepping motor 42BYG250A for use and is had the SH-20403 stepper motor drivers of 64 segmentations.Therefore the SH-20403 internal drive is isolated control signal and motor-driven, adopts NPN type triode 9013 to realize that control signals are connected with buffering between the single-chip processor i/o mouth.The drive part of color filter wheel and reflective mirror selects for use Seiko to become stepper motor driver SMD-401, this driver integrated level height, and it is big to drive phase current, adopts the DIP encapsulation, can be welded direct on the circuit board to improve integrated level.The control signal of SMD-401 driver adopts multichannel photoelectrical coupler TLP280 to carry out Signal Spacing owing to do not isolate.In order to realize the initial alignment of each stepper motor, adopt the integrated-type optical coupled switch to carry out position probing.Optical coupled switch output 5V voltage signal, the input voltage range of single-chip microcomputer IO mouth is 0～3.3V, therefore at first use low-voltage 74LV07 to realize interface between two kinds of voltage signals, adopt Schmidt trigger 74LV14 the input pulse signal to be carried out the I/O interface of input single-chip microcomputer after the shaping then.Stepper motor driver interface circuit and optocoupler testing circuit are as shown in Figure 5.
For data acquisition: many gratings autoscan spectrometer of design can be installed 3 blocks of gratings that the groove number is different simultaneously, can realize the automatic continuous sweep from the ultraviolet spectrum to the infrared range of spectrum.At present the most of receivers that adopt to accept spectral range limited, often need to change receiver when carrying out spectral scan.Trouble for fear of changing receptacle designs two exit slits, can select the outgoing direction of light by reflective mirror, adopts the two-channel independent passage to realize the two paths of data collection on the hardware circuit design.Consider the diversity of receiver output signal type and size, the two-way analog signal channel of design can realize that maximum 256 times of programmable-gain adjustment and current and voltage signals switch able to programme.The signaling interface front end adopts 5V dpdt relay OMRON2235 to realize that the software of voltage or electric current switches, in order to reduce the common mode interference in the signal transmission path, all adopt the difference input pattern for voltage signal and the amplification of current signal prime, operational amplifier adopts OP07, and electric current and voltage switching and differential amplifier circuit are as shown in Figure 6.In order to realize the programmable-gain of signal, post-amplifier adopts two programmable gain amplifier AD526 to be connected in series.Monolithic AD526 can provide 1,2,4,8 and 16 multiplication benefits, and two series connection can provide maximum 256 multiplication benefits.The gain control of AD526 adopts transparent mode, and 11 pins that are about to AD526 connect height, 13 and 14 pin ground connection.Two paths of signals needs 4 AD526 altogether, every AD526 needs 3 control signals, need 12 control signals altogether, therefore adopt 74HC164 to seal in and go out the interface that chip is realized itself and single-chip microcomputer, minimizing takies single-chip processor i/o, only needs 4 I/O lines both can realize the programmable-gain control of two paths of signals.The interface voltage of C8051 single-chip microcomputer is a 3.3V voltage, and the interface level of 74HC164 is a Transistor-Transistor Logic level, and the open collector chip 74LV07 of employing low-voltage realizes the interface between 3.3 level and the 5V level.The signal sampling channel theory of constitution as shown in Figure 7.
For hardware filtering: in order to eliminate the frequency alias noise that causes by the AD conversion, before entering the AD conversion, simulating signal use low-pass filter that input signal is carried out Filtering Processing, use second order Butterworth filter low-pass filter, designing it-the 3db cutoff frequency is 200KHz, AD converter adopts the 500KHz sample frequency that the simulating signal of input is changed.The second order Butterworth filtering circuit that uses as shown in Figure 8.
For usb circuit: owing to adopt the worm and gear kind of drive to drive grating rotating, the outgoing wavelength of monochromator becomes nonlinear relationship with the number of steps of stepper motor, upper computer software need calculate according to the relation of wavelength and step number, real-time passes to the slave computer control system with the pairing number of steps of wavelength increment, the control grating rotating, with the data upload of gathering, the data volume of system communication is bigger simultaneously.In order to improve data rate, control system adopts USB interface to be connected with computing machine, has overcome the restriction that original employing RS232 interface transmission speed reaches no hardware CRC slowly.Control system has kept the Debugging message output interface of RS232 interface as system.The CH372 that permanent Electronics Co., Ltd. produces oozes in USB interface chip employing Nanjing.C8051F060 adopts external memory interface to be connected with CH372, and interface circuit as shown in Figure 9.The external memory interface of C8051F060 can be positioned at port P3, P2, P1 and P0 or be positioned at port P7, P6, P5 and P4, selects high-end port by the PRTSEL position of configuration EMI0CF.Configuration EMD2=0, make port working on ground/data multiplex mode (address of separation and data pin), can save the P5 mouth like this with as universaling I/O port.The input/output port of C8051 single-chip microcomputer is configurable, by configuration register XBR0 and XBR1, UART0 and CEX0 is configured to the corresponding port, the interruption of CH372 is exported be configured to P0.4, and promptly external interrupt 0.
For software systems:
The slave computer software design: Integrated Development Environment Keil8.0 is adopted in the slave computer software exploitation.Use the JATG emulator EC3 of Silabs company to carry out system debug.The EC3 emulator is realized and the seamless link of Keil Integrated Development Environment by its driver EC3for Keil uVision3, is developed and debug very convenient.Slave computer software is mainly finished tasks such as system's parameters initialization, step motor control, data acquisition and USB interface communication.Initial work mainly contains: 1, cpu clock is selected outside 22.1184MHz crystal oscillator clock source; 2, the configuration cross bar switch is configured to P0.0 and P0.1 with TX0, the RX0 of UART0, and the outside output CEX0 of PCA0 is configured to port P0.2, and configuration P0.1 and P0.2 be for recommending output, and other pins are open-drain output, draws on a little less than enabling; 3, initialization UART0 uses timer 1 as Baud rate generator, and baud rate is 11.52K; 4, configuration ADC0 and ADC1 are single-ended input mode, and benchmark uses inner 2.4V bandgap reference voltage REF0 and REF1 respectively; 5, enable two-way DAC output, benchmark uses inner 2.4V benchmark REF2, and wherein DAC0 output is used for the adjusting control of the secondary high pressure of photomultiplier; 6, by external data bus initialization USB interface chip CH372, make it be operated in the external unit pattern, host computer can detect CH372 and its driver was installed automatically this moment; 7, initialization PCA0 is the programmable counter array, makes it be operated in 8 PWM modes, dutycycle position 50%, and counter/timer high byte PCA0H enables PCA0 and overflows interruption as the pulse number counter; 8, the grating turntable is rotated to the zero order light position; 9, color filter wheel and reflective mirror are navigated to initial position.After finishing, system initialization enters the order monitor state.Host computer sends to slave computer by USB interface with control command, interface chip CH372 makes single-chip microcomputer produce external interrupt 0 after receiving data, command buffer alignment is sent in the order that will receive in interrupting 0 service routine, is explained and carry out each bar order then by master routine.The key of system's control is to realize the at the uniform velocity rotation of grating turntable when carrying out spectral scan.In order to make motor in rotation, can carry out data acquisition simultaneously and to handle communication, improve sweep velocity, use the PCA0 of C8051F060 to control the rotation of grating motor automatically, PCA0 is set to 8 and is the PWM mode, dutycycle is 50%, the startup of control AD conversion in the PCA0 interrupt service routine.Automatically data are deposited in the disconnected therein service routine after AD converts and upload data queue, be responsible for sending data back to host computer, handle when having realized multitask by hardware mode by master routine.
The upper computer software design: use the software systems of Visual C++6.0 exploitation to have very high operational efficiency, therefore in order to improve the real-time of spectrometer control system, software Development adopts visual c++ 6.0.System software mainly comprises functions such as parameter setting, stop position control, length scanning, curve plotting, curve management, data preservation.System interface adopts the Multiple Document Interface framework that is similar to Visual C++6.0, and realizing on the left side, main interface can be in conjunction with floating frame, and with functions such as label mode switching controls, the management of scanner uni curve, the right side main window is used to draw scanning curve.System can open many history curves, and analyzes comparison under the same window.System can text, EXCEL and binary format are preserved data, makes things convenient for the data importing of third party software.
Handle for digital filtering: because most of light sources are subjected to the influence of power supply, when using spectrometer that spectroscopic data is scanned, in the result of data acquisition, often be doped with the 50Hz power frequency and disturb and the high frequency interference noise, in slave computer software, adopt the extreme value filter method to eliminate the 50Hz power frequency and disturb.Two yellow line 579.96nm and 579.07nm wavelength differ only 0.89nm in the low pressure mercury lamp standard spectral line, near the spectral line that does not adopt digital filtering to carry out continuous 10 scannings this two places wavelength location and to adopt digital filtering to carry out after continuous 10 scannings is compared, 10 scanning curves overlap substantially after adopting digital filtering, have obtained positive effect.Figure 10 is preceding 10 scanning results of filtering, and Figure 11 is continuous 10 scanning results after the filtering.
For calibrating method: the multiple-grating monochrometer that present embodiment provides, rotation by grating changes incident angle to obtain the monochromatic spectroscopic instruments of different wave length, its light path system generally adopts the Czerny-Turner structure, use two concave mirrors respectively as collimator objective and image-forming objective lens, guarantee that simultaneously the concave mirror center of curvature of two separation overlaps with same curvature radius.In order to increase diffraction intensity, system adopts reflective blazed grating as dispersion element.Derive according to C-T light channel structure and grating diffration theory, the corresponding relation of grating rotating angle and wavelength is:
mλ＝2dsinαcosθ(1)
Wherein θ is a fixed value, equates with half of incident light and emergent light angle, and α is that grating is begun the angle of being rotated by the zero order light position; M is that the level of diffraction light is inferior.Be zero order light when m=0,, be complex light because it has comprised all wavelengths.Generally select for use energy strong one-level light as emergent light.According to formula (1), get m=1, the step angle of stepper motor is γ, the segmentation of stepper motor driver is than being k
1, the ratio of gear of worm and gear is k
2, the step number that grating rotating is walked to the zero order light position is S0, and the step number that grating rotating is walked to a certain wavelength monochromatic light is S, and then the corresponding relation of step number and wavelength is
Except that λ was independent variable, all the other parameters were constant in the formula (2).Make A=180k
1k
2/ γ π B=1/2dcos θ, then (2) are reduced to:
S＝Aarcsin(Bλ)+S0(3)
Formula (3) is the final number of motor steps and the corresponding relation of outgoing wavelength, and wherein A, B, S0 are constant.
Use formula S=Aarcsin (B λ)+S0 to determine the wavelength of control grating rotating and the corresponding relation of stepper motor steps, wherein λ is an outgoing light wavelength behind monochromator splitting, A is for to segment the determined constant of stepper motor step angle when by worm gear transmission ratio, stepper motor, B is by apparatus structure and the determined constant of grating constant, and S0 is the step number of grating zero level optical position apart from mechanical zero.Constant A can obtain by calculating in the formula, and constant B and S0 need to obtain by calibrating method.
Use grating monochromator to be calibrated and custom-designed calibration software, with photomultiplier as receiver, mercury lamp standard spectral line is carried out continuous sweep, constant B and S0 among formula (3) S=Aarcsin (B λ)+S0 are demarcated, and use the standard spectral line of sodium vapor lamp that calibration result is verified.The catch that the new grating monochromator of installing requires the pattern zero point location to use must be installed between the 3rd block of grating and the first block of grating.At first the grating turntable is repositioned to mechanical zero before each scanning, be that the control step motor makes the catch on the grating turntable rotate to the optocoupler position, serve as control step motor rotation at interval with 16 steps then, the grating turntable is rotated a circle, come back to the optocoupler position up to locating stop piece, promptly use three blocks of gratings to finish scanning respectively same mercury lamp spectrum.In the scanning process, calibration software is with step number and gather numerical value with the real-time reading scan result of two-dimensional curve form, wherein horizontal ordinate is a step number, and ordinate is a spectral energy, and stepper motor is begun the step number walked by mechanical zero and the spectrum numerical value of collection saves as text.After run-down is finished, use calibration software that the data and curves that obtains is divided into three parts and analyze respectively, these three sections curves are respectively the scanning result of three pairing mercury lamp spectral lines of grating.At each section curve, with the strongest spectral position of the energy that occurs at first as zero order light, take this as the standard, the spectral line of close zero order light is the pairing spectral line of purple light 404.66nm, be respectively each bar spectral line such as 435.84nm, 546.07nm, 576.96nm and 579.07nm by that analogy, will comprise that the pairing stepper motor steps of each bar spectral line of zero order light is noted.Three blocks of gratings of quick acquisition zero order light separately that can be rough by above method scanning reaches and the pairing stepper motor steps of mercury lamp standard spectral line.Then at every block of grating, be the center with determined zero order light of said method and the pairing stepper motor steps of each standard spectral line respectively, at interval [S-128, S+128] serve as to rescan every spectral line at interval in the scope with a step, number of motor steps and corresponding spectral line collection result are noted, and therefrom found out maximal value, this process repeats 10 times, to obtaining 10 groups of stepper motor steps by position of spectral line, that 10 groups of numbers are average back as the final pairing stepper motor steps of this spectral line.It is pairing for obtaining the step number S0 that zero order light should walk and obtaining the step number S that mercury lamp standard line wavelength should be walked to obtain every block of grating installing respectively by above method.
With the stepper motor steps mean value of zero order light correspondence as S0, bring the step number mean value and the wavelength of each bar spectral line correspondence into formula B=(sin (S-S0/A))/λ, parameter A is determined by machinery segmentation and electric segmentation ratio, calculate the pairing B parameter of each standard spectral line respectively, undertaken after the geometric mean as the B parameter of using in the final formula by 5 B parameter then.Simultaneously, after parameters is determined in the formula, use two spectral line 589nm of low-pressure sodium lamp and 589.6nm formula to be calibrated as the calibration spectral line.Experimental result shows, segments multiple-grating monochrometer for 180: 1 machinery segmentations and 64: 1 electricity, can reach the listed bearing accuracy of Figure 13 fully.
Calibrating method for example; The step angle of the stepper motor of selecting is 1.8 °, and worm gear transmission ratio is 180: 1, and stepper motor segments than being 64: 1, can determine constant A=366693 in the formula (3).Owing to have certain mismachining tolerance and alignment error in the production run, the parameter of determining in the time of can not using Design of Mechanical Structure is come constant B and the S0 in the computing formula (3), uses the special use calibration software of design by said method constant B and S0 to be demarcated again.Figure 14 scans the relation that the back obtains mercury lamp spectral line and step number for using 1200 ruling gratings, and Figure 15 obtains constant B for calculating, and being averaged is worth B=0.00063097964.Making uses the same method can determine the employed constant B of different grating constants.To calculate the constant A that obtains and test the constant S0 and the B that obtain and bring formula (3) into, use 1200 ruling gratings that the precision of low-pressure sodium lamp spectral line with 0.01nm scanned, can differentiate two two D spectral lines of 589nm and 589.6nm very clearly, as shown in figure 11, experimental results show that the control accuracy that can reach 0.01nm.
Obtain 5 constant B respectively as shown in figure 15 according to the data computation among Figure 14, the B=0.0006309797 that averages.
Claims (5)
1. the calibrating method of a multiple-grating monochrometer, it comprises uses grating monochromator to be calibrated and calibration software,, it is characterized in that as receiver with photomultiplier:
Mercury lamp standard spectral line is carried out continuous sweep, constant B and S0 among formula S=Aarcsin (B λ)+S0 are demarcated, and use the standard spectral line of sodium vapor lamp that calibration result is verified; Wherein λ is an outgoing light wavelength behind monochromator splitting, the step number of pairing stepper motor when S is λ for the outgoing wavelength, and A is determined the A=180k in the formula by segmented when the stepper motor step angle by worm gear transmission ratio, stepper motor
1k
2/ γ π, the step angle of stepper motor are γ, and the segmentation of stepper motor driver is than being k
1, the ratio of gear of worm and gear is k
2, B is the constant of being determined by grating constant and monochromator light path system, S0 be grating by mechanical zero rotate to the zero order light position the stepper motor steps that should walk; Constant A can obtain by calculating in the formula, and constant B and S0 need to obtain by calibrating method; Use formula S=Aarcsin (B λ)+S0 to realize the accurate wavelength control of grating monochromator; The catch that the pattern zero point location of the grating monochromator newly installed is used is installed between the 3rd block of grating and the first block of grating; At first the grating turntable is repositioned to mechanical zero before each scanning, be that the control step motor makes the catch on the grating turntable rotate to the optocoupler position, serve as control step motor rotation at interval with 16 steps then, the grating turntable is rotated a circle, come back to the optocoupler position up to locating stop piece, promptly use three blocks of gratings to finish scanning respectively same mercury lamp spectrum; In the scanning process, calibration software is with step number and gather numerical value with the real-time reading scan result of two-dimensional curve form, wherein horizontal ordinate is a step number, and ordinate is a spectral energy, and stepper motor is begun the step number walked by mechanical zero and the spectrum numerical value of collection saves as text; After run-down is finished, use calibration software that the data and curves that obtains is divided into three parts and analyze respectively, these three sections curves are respectively the scanning result of three pairing mercury lamp spectral lines of grating; At each section curve, with the strongest spectral position of the energy that occurs at first as zero order light, take this as the standard, the spectral line of close zero order light is the pairing spectral line of purple light 404.66nm, be respectively each bar spectral line of 435.84nm, 546.07nm, 576.96nm and 579.07nm by that analogy, will comprise that the pairing stepper motor steps of each bar spectral line of zero order light is noted; Three blocks of gratings of quick acquisition zero order light separately that can be rough by above method scanning reaches and the pairing stepper motor steps of mercury lamp standard spectral line; Then at every block of grating, be the center with determined zero order light of said method and the pairing stepper motor steps of each standard spectral line respectively, at interval [S-128, S+128] serve as to rescan every spectral line at interval in the scope with a step, number of motor steps and corresponding spectral line collection result are noted, and therefrom find out maximal value, this process repeats 10 times, to obtaining 10 groups of stepper motor steps by position of spectral line, that 10 groups of numbers are average back as the final pairing stepper motor steps of this spectral line with the intermediate value method of average; It is pairing for obtaining the step number S that mercury lamp standard line wavelength should be walked to obtain every block of grating installing respectively by above method; To every block of grating, with the stepper motor steps mean value of zero order light correspondence as S0, bring the step number mean value and the wavelength of each bar spectral line correspondence into formula B=(sin (S-S0/A))/λ, parameter A is determined by machinery segmentation and electric segmentation ratio, calculate the pairing B parameter of each standard spectral line respectively, undertaken after the geometric mean as the B parameter of using in the final formula by 5 B parameter then; Simultaneously, after parameters is determined in the formula, use two spectral line 589nm of low-pressure sodium lamp and 589.6nm formula to be calibrated as the calibration spectral line.
2. the calibrating method of a kind of multiple-grating monochrometer according to claim 1, the calibrating method that it is characterized in that described multiple-grating monochrometer has used a kind of multiple-grating monochrometer, it mainly comprises monochromatic beam splitting system, control system, computing machine and printer, it is characterized in that monochromatic beam splitting system and Control System Design are one, instrument top is grating chamber, and the bottom is the controller chamber; Grating chamber mainly comprises an entrance slit, two exit slits, color filter group, two concave mirrors, grating turntable, reflective mirror and stepper motors, and the folding size of incident and exit slit is by manual control; Hardware circuit adopts second order Butterworth wave filter to carry out anti-aliasing filter, eliminates 200KHz with upper frequency, adopts the extreme value filter method to eliminate by the 50Hz power frequency of light source power supply system introducing in the software design and disturbs; Use 8 pulse duration modulation methods of hardware to realize to Stepping Motor Control, negative edge in pulsewidth output produces hardware interrupts, interrupt service routine withdraws from after starting the AD conversion, by AD conversion interrupt service routine sampled result is sent into the data buffering formation behind the AD EOC, realized multi-task mechanism by hardware mode.
3. the calibrating method of a kind of multiple-grating monochrometer according to claim 2, the calibrating method that it is characterized in that described multiple-grating monochrometer has used a kind of multiple-grating monochrometer, described two exit slits are installed two kinds of receivers simultaneously, the color filter wheel of six groups of color filters that incident light spectrum is filtered is installed at the entrance slit place, the grating of an above different wavelength range is installed on the grating turntable, the grating turntable adds worm and gear by stepper motor and drives, the pulpit is mainly by control circuit, and stepper motor driver and power supply are formed.
4. the calibrating method of a kind of multiple-grating monochrometer according to claim 1, the calibrating method that it is characterized in that described multiple-grating monochrometer has used a kind of multiple-grating monochrometer, its control is gathered integrated, the design of control circuit and data acquisition circuit merges on the circuit, and will control and Acquisition Circuit is installed in the bottom of monochromator casing; Control system adopts the usb bus interface to connect computing machine, by computer realization to the real-time control of grating turntable, color filter automatically or manual switching, integrated signal gathering unit can be gathered voltage or current signal, have 1 times～256 times programmable-gains, the trigger port that has two-way is simultaneously realized the real-time control and the high speed spectrum data scanning of automatic grating monochromator.
5. the calibrating method of a kind of multiple-grating monochrometer according to claim 1, the calibrating method that it is characterized in that described multiple-grating monochrometer has used a kind of multiple-grating monochrometer, described grating turntable adopts three optical grating constructions, between the 3rd block of grating and first block of grating the catch that the pattern zero point location uses is installed; Control system is that core realizes adopting USB interface to be connected with computing machine to the control and the double channel data acquisition of grating turntable, color filter wheel, reflective mirror with the C8051F060 single-chip microcomputer; The signal condition unit connects photomultiplier, photoelectric cell receiver.
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